I live in Southern Ontario and considering Mobil 1 10w30 or Castrol 5w50. This oil change will take me well into the winter but there is still some hot weather comeing up as well. Also, all of the Synthetics except the Castrol are of the "Energy Saving" variety. What's the diff??

KraTOR,

From one Canuc to another: You've been around long enough to know that the oil issue is a hot button for some folks. I'll keep it basic, but the archives are full of more detailed explanations and some specific chemistry to back up what I'm about to repeat.

For your purposes the 10w30 is ample, you can even go to the 5w30 as the specs are virtually identical in the Mobil 1 line. The 5w30 is in fact what Audi advises in the manual, and the synthetic is an order of magnitude better than the basic dino for hot/cold extremes.

The US energy conserving std. replaces the old energy conserving II. Basically it has less friction, saving gas, and fewer extenders, cleaner emmissions.

I would agree that 10W-30 or 5W-30 energy-saving synthetic is fine. Also the Castrol 5W-50 should be OK too. I have not seen any energy conserving oils in the higher viscosities so I suspect that is a factor in why Castrol 5W-50 is not E.C..